Induction of nuclear NF-kappa B DNA binding activity after exposure of lymphoid cells to soluble tax1 protein

We demonstrate that purified HTLV-I Tax1 protein can be taken up by 70Z/3 lymphoid cells and localized in both the nuclear and cytoplasmic compartments. Introduction of the Tax1 protein into the growth medium of 70Z/3 cells resulted in the rapid and transient induction of NF-kappa B binding activity in the nuclear fraction. Tax1 activation of NF-kappa B was not sensitive to either staurosporin or prolonged stimulation with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate, suggesting that Tax1-dependent NF-kappa B activation did not require the protein kinase C pathway. Purified Tax1 did not directly increase NF-kappa B binding activity in 70Z/3 cytoplasmic extracts, suggesting that NF-kappa B induction may require cellular factors. Western blot and competitive radioimmunoassays demonstrated that Tax1 protein was present in the tissue culture media of HTLV-I-transformed cell lines. These results show that extracellular Tax1 may regulate cellular gene expression in noninfected cells.     

Characterisation of NF-kappa B complexes in Theileria parva-transformedT cells

Transformation of T cells by the intracellular parasite Theileria parva is accompanied by constitutive I-kappa B degradation and NF-kappa B activation, a process which is essential to prevent the spontaneous apoptosis of these parasite-transformed cells. NF-kappa B-mediated responses are regulated by selective combinations of NF-kappa B proteins as homo- or heterodimers and by distinct kappa B motifs. We characterised the NF-kappa B complexes induced by T. parva infection in TpM(803) T cells. By western blot, we demonstrated that all members of the NF-kappa B/Rel family of proteins translocate to the nucleus of infected cells. Using two different kappa B oligonucleotides (kappa B-1 and kappa B-2), both containing the decameric consensus kappa B motif (GGGACTTTCC), clearly distinct patterns of DNA binding activities could be demonstrated in electrophoretic mobility shift assays. Supershift analysis and UV cross-linking assays showed that complexes binding to kappa B-1 consisted of p50, p65 and RelB homo and/or heterodimers. We could also detect an association of ATF-2 and c-Fos with one of the complexes. The HIV-derived kappa B-2 oligo only bound p50 and p65. Additionally, several agents known to inhibit a wide range of NF-kappa B activation pathways had no inhibitory effect on the activation of NF-kappa B DNA binding in TpM(803) T cells.     

Differential roles for NF-kappa B in endotoxin and oxygen induction of interleukin-8 in the macrophage

The alveolar macrophage is an important source of interleukin (IL)-8 during pulmonary injury. The IL-8 gene promoter sequence contains nuclear factor (NF)-kappa B, NF-IL6, and activator protein (AP)-1 binding sequences. These sites may have differing regulatory roles in hyperoxia-exposed macrophages than in those stimulated by bacterial lipopolysaccharide (LPS). U-937 and THP-1 macrophage-like cells were exposed to air-5% CO2 or 95% O2-5% CO2, with or without 1.0 microg/ml of LPS, and transfected with an IL-8 promoter-reporter containing NF-kappa B, NF-IL6, or AP-1 mutations. Hyperoxia and LPS caused additive increases in IL-8 production by U-937 cells, whereas THP-1 cells responded only to LPS. An NF-kappa B mutation ablated baseline and O2- and LPS-stimulated reporter activity in both cell lines, whereas NF-IL6 mutations had little effect. An AP-1 mutation had an intermediate effect. LPS, but not hyperoxia, stimulated nuclear translocation of NF-kappa B in both cell lines. Pharmacological blockade of NF-kappa B nuclear translocation ablated LPS-, but not hyperoxia-, stimulated IL-8 production. Although an intact promoter NF-kappa B site is crucial to macrophage IL-8 production, only LPS-stimulated production appears to require additional nuclear translocation of NF-kappa B.     

Theileria-induced constitutive IKK activation is independent of functional Hsp90

The intracellular parasite Theileria induces uncontrolled proliferation and host cell transformation. Parasite-induced transformation is accompanied by constitutive activation of IkappaB kinase (IKK), resulting in permanently high levels of activated nuclear factor (NF)-kappaB. IKK activation pathways normally require heat shock protein 90 (Hsp90), a chaperone that regulates the stability and activity of signalling molecules and can be blocked by the benzoquinone ansamycin compound geldanamycin (GA). In Theileria-transformed cells, IkappaBalpha and p65 phosphorylation, NF-kappaB nuclear translocation and DNA binding activity are largely resistant to GA and also NF-kappaB-dependent reporter gene expression is only partly affected. Our findings indicate that parasite-induced IKK activity does not require functional Hsp90.